In the related art, as disclosed in the International Publication No. WO2013/021497, a seat is known in which a seating part is supported to be pivotally movable with respect to a support member extending rearward and upward. The seat is configured so that a front side of the seating part is supported and a rear side thereof is in a freely movable state. That is, the front side of the seating part is supported in a cantilever manner.